Volume 517 Number 7532 pp6-116

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Dunes on Titan in a Cassini radar mapper image taken on 21 December 2008 (upper part of image) resemble those in Conception Bay in the Namib desert, seen here from 283 km altitude in NASA crew image STS107-E-5380 (lower part of image). NASAs Cassini spacecraft mission  still out there sending data from the Saturnian system  has revealed extensive aeolian (wind-formed) dunes on the surface of Titan, Saturns largest satellite. Devon Burr et al. used a high-pressure wind tunnel to simulate the thick near-surface atmosphere on Titan and, with numerical modelling of the low gravity and low sediment density, derived the wind speeds necessary to move dune sand on Titan. These speeds are significantly higher than those predicted by present models of sediment entrainment by wind that are based on wind-tunnel experiments under conditions relevant for Earth and Mars. Experimental results and theoretical work can be reconciled if the extremely low ratio of particle to fluid density on Titan is taken into account, a correction that is not required for high density ratio environments such as jets on comets. Cover: NASA/JPL-Caltech/ASI/ Johnson Space Center

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Explore the gory glories of forensic science, grapple with Tom Stoppard's take on consciousness, learn what it takes to live on Mars, re-enter Jurassic Park, dive into a coral reef and dally with Robert Oppenheimer. Daniel Cressey reports.

Using electron cryomicroscopy, the structure of the rabbit RyR1 calcium channel is determined at 6.1 Å resolution in the closed state and 8.5 Å in the open state, revealing how calcium binding to the EF-hand of RyR1 regulates channel opening and facilitates calcium-induced calcium release.

Using electron cryomicroscopy, the closed-state structure of rabbit RyR1 is determined at 4.8 Å resolution; analysis confirms that the RyR1 architecture consists of a six-transmembrane ion channel with a cytosolic α-solenoid scaffold, and suggests a mechanism for Ca2+-induced channel opening.

Using electron cryomicroscopy, the structure of the closed-state rabbit ryanodine receptor RyR1 in complex with its modulator FKBP12 is solved at 3.8 Å; in addition to determining structural details of the ion-conducting channel domain, three previously uncharacterized domains help to reveal a molecular scaffold that allows long-range allosteric regulation of channel activities.

Laboratory measurements of iron opacity made under conditions similar to those inside the Sun reveal much higher opacity than predicted, helping to resolve inconsistencies within stellar models of the internal temperatures of stars.

Wind tunnel experiments designed to simulate the conditions on Saturn’s moon Titan yield threshold wind speeds for particle saltation higher than those predicted by models derived from simulations of terrestrial-planet conditions; the results can be reconciled by modifying the models to take into account the low ratio of particle density to fluid density on Titan.

Quantized conductance in the transport of neutral atoms is observed in an optically produced channel — either a quantum point contact or a quantum wire — between two atom reservoirs; the lowest non-zero conductance value is the universal conductance quantum, the reciprocal of Planck’s constant.

Usually materials design focuses on attractive interactions, but here a hydrogel is described whose properties are dominated by electrostatic repulsion between negatively charged titanate nanosheets embedded within it; the material, inspired by articular cartilage, deforms easily when sheared parallel to the sheets but resists compressive forces applied orthogonally.

Reconstruction of the Atlantic meridional overturning circulation from a highly resolved marine sedimentary record shows that a deep, vigorous overturning circulation mode has persisted for most of the last glacial cycle, dominating ocean circulation in the Atlantic, but that a shallower glacial mode prevailed during glacial maxima.

A comparison of protein-coding genes from 134 archaeal genomes with their homologues in 1,847 bacterial genomes reveals that, during evolution, genes are transferred more often from bacteria to archaea than vice versa, and that gene influxes from bacteria can bring about the origin of major archaeal groups.

Using transplantation and lineage-tracing strategies, protein C receptor is identified as a marker of mammary stem cells in mice, with potential implications for understanding the initiation of breast cancer.

Hepatitis A virus is a picornavirus that causes significant morbidity but remains poorly understood; this paper now provides high-resolution crystal structures of both the mature and the empty hepatitis A virus particle, which show that the three-dimensional structure resembles insect picorna-like viruses.

The activation and coordination of phosphatase activity is important during mitotic exit; here, a mitotic phosphatase relay is described in fission yeast between the two major phosphatases, PP1 and PP2A, a mode of regulation that may be a feature of signalling networks across eukaryotes.

The radiation-damage-free structure of the photosystem II membrane protein complex, which oxidizes water into dioxygen in an oxygen evolving complex, has been determined by an X-ray free electron laser at a resolution of 1.95 Å; one of the substrate oxygen atoms in this reaction is now identified.

Solving the X-ray crystal structure of a Δ14-sterol reductase and homologue of human C14SR and DHCR7, two enzymes that reduce specific carbon–carbon double bonds in the cholesterol biosynthetic pathway, may provide insight into how specific mutations in DHCR7 and lamin B receptor lead to human diseases.